Extraction of dyewood



Cet. l0, 1944.l l RL. DREW 2,360,114

EXTRACTION 0F DYEWOOD Filed Sept. 30, 1941 57i/W WATER f L l EWI/701749701? ATTORNEYS Patented Oct. 10, 1944 UNITED STATES PATENT 4OFFICE EXTRACTION OF DYEWOOD Application September 30, 1941, Serial No. 412,963

(Cl. MiO-333) Claims.

This invention relates to the extraction of dyewoods and particularly to the preparation of pure extracts free from wood sugars, tanning, materials, and other inert substances. While the invention will be described more particularly in connection with the treatment of logwood, it may be utilized in preparing similar extracts of other dyewoods such as Vhypernic, fustic and osage.

The extraction of dyewoods is a relatively old l art which has been conducted on a commercial scale for many years. The procedure heretofore followed is extremely simple. The dyewood is chipped and digested'with water and steam until the water soluble content of vthe chips yhas been extracted. The chips are discardedandthe ,extract, con-taining wood sugars, tanning materials and other inert substances soluble in `water are then concentrated by evaporation to aord a material of the consistency of thin molasses. This product, contaminated with the water `soluble constituents of the wood, has been supplied to the trade and utilized without further purication for the purposes for which dyewood extracts are commonly'used.

The coloring Vmaterial in logwood is haematoxylin. In the `form in which the heavy extract has rbeen supplied to the trade heretofore, the Value of the haematoxylin Vas a coloring agent has been reduced somewhat by the presence of the impurities mentioned. However, there has been heretofore no practicable commercial method which permitted separation of the contaminating materials in an economical manner and hence pure haematoxylin has not been available except in smal1amounts produced by elaborate laboratory methods.

It is the object of the present invention to provide a simple and effective commercial method of recovering coloring materials from dyewoods free from contamination with wood sugars, tanning Amaterials and other Vinert substances.

Another object of the invention is the provision of an economical method of preparing substantially pure haematoxylin from logwood.

Other objects and advantages of the invention will be apparent as it is lbetter understood by reference to the following specification and the accompanying drawing, which diagrammatically illustrates, in the form of a flow sheet, an apparatus and procedure Vadapted for the accomplishmentof the purpose of the invention. Details of the apparatus familiar to those skilled inthe art have been omitted for Ythe purpose of clarity,

I have discovered that haematoxylin, in the presence `of wood sugars and the like, has a prefl erential solubility in certain organic solvents,

and that it may be separated from water solutions by treatment with such solvents. l have further discovered that in the absence of wood sugars and the like, haematoxylin exhibits a preferential solubility in water so that it may be separated from the organic'solvent by treatment with Water. These discoveries aiord the basis for a simple and effective procedure for the recovery of substantially pure haematoxylin from the heavy extract produced by digestion of the dyewood chips with water. Thus, in the practice of the invention, I carry out the usual digestion of the chips in water with steam, and separate the extract from the chips. Theextraot is then concentrated by evaporation in the usual manner. The heavy extract Ais then agitated witha suitable solvent. Such a solvent should be `substantially immiscible with `Water and a solvent which will separate the haematoxylin from the wood sugars, tanning materials and the like, which are insoluble in the solvent. ,Normal butyl alSIQhol has in practice-provedto bethe most satisfactory solvent. Other solventssuch as methyl ethyl ketone, furfural, tertiary amyl valcohol and secondary butyl alcohol are among other available solvents. There are, of course, many commercial organic solvents, and any such solvent having the desired properties 4could be employed. Hence the list of solvents herein mentioned is not exhaustive.

Following the treatment of the heavy extract with the organic solvent, the latter, containing the haematoxylin, can be separated readily, 4by settling or otherwise, in a suitable separator. The water layer containing the .wood sugars, tanning materials and other impurities, is discarded. The layer containing the haematoxylin is withdrawn and agitated with Water which, `as previously indicated, again takes up the haematoxylin which is preferentially soluble in the Water in the absence of the impurities which have been removed. Following agitation, the liquor may be again separated yby gravity or otherwise. The organic solvent, now substantially free from haematoxylin, is sent to a solvent recovery still where the solvent is recovered for Vfurther use,the residue being discarded. The Water layer containing the haematoxylin issubjected toevaporation to produce a heavy extract of haematoxylin which is free `from .the impurities .originally present. This liquor maybe `utilized for the purposes for which the impure heavy `extract `has vbeen previously employed. Obviously, :because .of .the elimination of impurities, it affords a more desir.- able and satisfactory product, in which the color for further use. The residue, consisting of water,

is discharged.

Except in the initial stage of extracting the chips, the temperature at which the operation is conducted may be varied widely, so long as the boiling point of the solvent is not exceeded. The operations may be conducted successfully at ordinary room temperature or even at considerably lower temperatures. The temperatures may be raised above room temperature to accelerate the operation if such acceleration is desirable. The time of contact between the organic solvent and the heavy extract, and the time of treatment of the organic solvent with water, are likewise subject to wide variation. The time for each of these operations can be controlled readily to obtain the desired result.

In order that the invention may be more clearly understood, reference is made to the drawing, in which indicates the chip digester to which water and steam are introduced through pipes indicated at 6 and 1. The spent chips are discharged after suitable treatment. The extraction of the chips consumes normally about twentyfour hours, or more or less time may be required, depending upon the character of the chips treated. The operation is in all respects com-` l parable with the well known digestion treatment which has been practised for many years.

In accordance with the invention, the liquor from the digester 5.is conveyed through a pipe 8 to an evaporator 9. Any suitable type of evaporator may be used. The heavy extract is delivered through a pipe I0 to an extractor II having an agitator I2 driven by a motor I3 or from any suitable source of power. The solvent, for example normal butyl alcohol, is supplied from a storage tank I4 through a pipe I5. Agitation of the heavy extract with the organic solvent results, as hereinbefore stated, in the selective solution of the haematoxylin, leaving the wood sugars, tanning material, etc., in the water.

Thewater and organic solvent pass through a pipe IB to a separator I1. Any suitable separator may be employed. When separation is effected, the water is discharged through a pipe I8 and the organic solvent carrying the haematoxylin passes through a pipe I9 into a second extractor 2D. This likewise is provided with an agitator 2l driven by a motor 22 or any other suitable source of power. Waterris introduced through a pipe 23, and agitation is continued until the haematoxylin has again been dissolved in the water.

The mixture of organic solvent and water is then conveyed through a pipe 24 to a separator 25 of any suitable form. The solvent layer from the separator, which isnow freed from haematoxylin, is discharged through a pipe 26 to a solvent recovery still 21 from which the solvent is withdrawn through a pipe 28. The solvent may be returned to the storage tank I4. The 75 residue from the still is discharged through a pipe 29.

The water layer from the separator 25 -carrying the haematoxylin passes through a pipe 30 into an evaporator 3l. Any suitable type of evaporator may be used. The purified heavy extract is withdrawn through the pipe 32. This extract, as hereinbefore indicated, is free from wood sugars, tanning materials and the like, and constitutes a superior product adapted forthe uses of haematoxylin solutions. Crystalline haematoxylin can be recovered therefrom by crystallization, and if purer forms are required, recrystallization will result in the separation of any minute proportions of impurities which may be present.

In order that none of the solvent may be l-ost, the evaporate is conducted through a pipe 32 to a solvent recovery still 33 in which the solvent is withdrawn through a pipe 34. The sclvent may be returned to the storage tank I4. 'Ihe residue escapes through a pipe 35.

As hereinbefore indicated, the temperature and time of extraction are not critical in the foregoing operations. Except for the use of steam in the initial digestion of the chips and the application of heatl in the evaporator 3l, and the recovery stills 21 and 33, the various operations may be conducted satisfactorily at room or higher or lower temperatures as may be desired. The invention resides, therefore, in the practical application of the preferential solubilities of the haematoxylin in organic solvents and in water according to the particular conditions with respect to the presence or absence of wood sugars and other impurities in the extract.

Various changes may be made in the procedure and particularly in the details of the apparatus and the operation without departing vfrom the invention or sacrificing any of the'advant'ages thereof.

I claim: Y

l. The steps in the method of extracting dyewood which comprise treating a crude vwater extract of the dyewood with an organic solvent substantially immiscible with water and having a preferential solvent effect on the coloring constituent of the dyewood, separating the organic solvent, and then extracting the solvent with water to recover the coloring constituent in water solution.

2. The steps in the method of extracting dyewood which comprise treating a crude water extract of the dyewood with an organic solvent from the class including normal and secondary butyl alcohols, methyl ethyl ketone, furfural and tertiary amyl alcohol, separating the organic solvent and then extracting the solvent with water to recover the solvent-and the coloring constituing constituent, separating and discarding the water solution, retaining the impurities and eX- tracting the organic solvent with water to recover the solvent and theY coloring constituent of Y the dyewood in Watersolution.

4. The method of separating the coloring constituent of dyewood from impurities present in a crude water extract thereof which comprises treating the crude Water extract with an organic solvent substantially immiscible with Water and having a preferential solvent eiect on the coloring constituent, separating and discarding the Water solution, retaining the impurities, extracting the organic solvent with Water to recover the solvent and the coloring constituent of the dyewood in water solution, and recrystallizing the Water solution to separate pure crystals of the coloring constituent.

5. The method of separating the coloring constituent of dyevvood from impurities present in a crude Water extract thereof Which comprises treating the crude water extract with an organic solvent from the class including normal and secondary butyl alcohols, methyl ethyl ketone, furfural and tertiary amyl alcohol, separating and discarding the Water solution, retaining the impurities and extracting the organic solvent with Water to recover the solvent and the coloring constituent of the dyevvood in Water solution.

6. The method of separating the coloring constituent of dyewood from impurities present in a crude water extract thereof which comprises treating the crude Water extract with an organic solvent from the class including normal and secondary butyl alcohols, methyl ethyl ketone, furfural and tertiary amyl alcohol, separating and discarding the water solution, retaining the impurities, extracting the organic solvent with water to recover the solvent and the coloring constituent of the dyevvood in Water solution, and recrystallizing the Water solution to separate pure crystals of the coloring constituent.

7. The method of eliminating impurities from crude dyewood Water extract which comprises treating the crude extract with an organic solvent substantially immiscible with Water and selectively eiective to dissolve the coloring constituent of the dyevvood, discharging the Water carrying the impurities, extracting the organic solvent with water to separate the coloring constituent and recovering the organic solvent for further use.

8. The method of eliminating impurities from crude dyewood Water extract which comprises treating the crude extract with an organic solvent from the class including normal and secondary butyl alcohols, methyl ethtyl ketone, furfural and tertiary amyl alcohol, discharging the Water carrying the impurities, extracting the organic solvent with Water to separate the coloring constituent and recovering the organic solvent for further use.

9. The method of eliminating impurities from crude dyevvood Water extract which comprises treating the crude extract with an organic solvent substantially immiscible with water and selectively eiTective to dissolve the coloring constituent of the dyevvood, discharging the Water carrying the impurities, extracting the organic solvent with Water to separate the coloring constituent, recovering the organic solvent for further use, and recrystallizing the Water solution to separate pure crystals of the coloring constituent.

10. The method of separating substantially pure haematoxylin from crude haematoxylin water extract which comprises treating the crude extract `vvith a Water immiscible organic solvent for haematoxylin, separating the Water containing the impurities in solution and extracting the organic solvent with water to redissolve the haematoxylin in water.

11. 'I'he method of separating substantially pure haematoxylin from crude haematoxylin water extract which comprises treating the crude extract with an organic solvent for haematoxylin from the class including normal and secondary butyl alcohols, methyl ethyl ketone, furfural and tertiary amyl alcohol, separating the Water containing the impurities in solution and extracting the organic solvent With water to redissolve the haematoxylin in water.

12. The method of separating substantially pure haematoxylin from crude haematoxylin water extract which comprises treating the crude extract with a water immiscible organic solvent for haematoxylin, separating the Water ycontaining the impurities in solution, extracting the organic solvent with water to redissolve the haematoxylin in water, and recrystallizing the Water solution to separate pure crystals olf the coloring constituent.

13. The method of separating substantially pure haematoxylin from crude haematoxylin Water extract Which comprises treating the crude extract with an organic solvent for haematoxylin from the class including normal and secondary butyl alcohols, methyl ethyl ketone, furfural and tertiary amyl alcohol, separating the water containing the impurities in solution, extracting the organic solvent with Water to redissolve the haematoxylin in Water, and recrystallizing the Water solution to separate pure crystals of the coloring constituent.

14. The method of separating substantially pure haematoxylin from crude haematoxylin Water extract which comprises treating the crude extract with a. Water immiscible organic solvent for haematoxylin, separating the Water containing the impurities in solution, extracting the organic solvent with Water to redissolve the haematoxylin in Water, and separating and recovering the organic solvent.

l5. The method of separating substantially pure haematoxylin from crude haematoxylin Water extract which comprises treating the crude extract With an organic solvent for haematoxylin from the class including normal and secondary butyl alcohols, methyl ethyl ketone, furfural and tertiary amyl alcohol, separating the Water containing the impurities in solution, extracting the organic solvent with Water to redissolve the haematoxylin in Water, and separating and recovering the organic solvent.

RAYMOND L. DREW. 

